Whether an operating force required to operate any of various instruments including the steering wheel of an automobile is appropriate for a driver's (operator's) specific force characteristic is conventionally evaluated based on the experiences of a person who provides an evaluation, in most cases by a sensory evaluation. Other evaluations include, for example, one of steering feeling using a myoelectric potential (see the Patent Document 1 and the Patent Document 2).
The Patent Document 1 describes an electric power steering apparatus. That document refers to a problem associated with prior art that a steering assist force is determined without considering the driver's human characteristic or, more specifically, the driver's force characteristic and, in addition, some drivers do not have a comfortable steering feeling. In order to solve the problem, the document describes an invention related to an electric power steering apparatus.
The electric power steering apparatus described in the Patent Document 1 produces the steering assist force using a torque generated by an electric motor and comprises force characteristic detecting means for detecting the driver's force characteristic and means for changing steering assist force generated by the electric motor according to the force characteristic detected by the force characteristic detecting means, whereby the force characteristic detecting means measures the load on a muscle of the driver through myoelectric measurement to determine the force characteristic.
According to the Patent Document 1, the steering assist force is changed according to the force characteristic that is detected as the driver's specific information. Thus, a steering assist force that best suits the driver can be imparted to the steering mechanism, and the driver can have a comfortable steering feeling.
The electric power steering apparatus described in the Patent Document 1 comprises a sensor for detecting the driver's force characteristic including electrodes disposed on the steering wheel and an impedance converter connected to the electrodes. When the driver holds the steering wheel, the palms of the driver's hands come into contact with the electrodes. The electric potential in the driver's body detected by the electrodes varies with the contact ratio, the contact pressure, etc. The driver's force characteristic is detected from the variation in the electric potential in his/her body.
The Patent Document 2 describes a steering feeling measuring apparatus for objectively and accurately evaluating the driver's steering feeling by differentiating between active steering and passive steering.
The steering feeling measuring apparatus described in the Patent Document 2 comprises first biological information detecting means for detecting first biological information produced by steering achieved as intended by the driver, second biological information detecting means for detecting second biological information that is other information than is produced by the steering achieved as intended by the driver, gathering means for gathering the first biological information detected by the first biological information detecting means and the second biological information detected by the second biological information detecting means by correlating the first biological information with the second biological information, and vehicle steering status detecting means for detecting the status of a steering mechanism of the vehicle driven by the driver. The gathering means further gathers information on the status of the vehicle steering mechanism together with the first biological information detected by the first biological information detecting means by correlating the information on the status of the vehicle steering mechanism with the first biological information. The first biological information is myoelectric potentials of the deltoid muscles and the second biological information is myoelectric potentials of the ulnar flexor muscles of wrist, pressures and slipping forces at given positions of both hands holding the steering wheel, etc.    [Patent Document 1] JP 11-321671 A    [Patent Document 2] JP 2003-177079 A